This invention relates generally to metallic cables suitable for reinforcing elastomeric articles, and more specifically to a cable structure and an apparatus and method for manufacturing a cable with this new structure.
One of the problems that may be encountered in elastomeric articles that are reinforced with metallic cables is the propogation of corrosion along the length of the cable in the event that the article is cut or torn so that the cable is exposed. One approach to solving the problem of corrosion propogation has been to make the cable very compact, so that there are no interstices between the filaments and strands comprising the cable, therefore leaving no natural pathway along which corrosion may travel. A second approach has been to make the cable with a very open construction, such that the elastomeric material in which the cable is embedded can penetrate the cable and substantially surround each individual filament. The present invention is concerned with the latter approach.
There has already been disclosed in U.S. Pat. Nos. 3,700,012 and 3,763,683 a method and apparatus for providing a cable of helical wire filaments that are nested in bundles and encapsulated within an elastomeric material to provide a reinforced fabric. The wire filaments are not twisted about one another, and no wrapping filament holds the helical filaments together, so the cable must be immediately encapsulated in the elastomeric material as a part of the same manufacturing process. The inability to store the cable itself on spools means each production line must comprise a cable forming apparatus in addition to an encapsulating apparatus, such as a calender, which is very costly and may require inordinately long set-up time between production runs.
A solution to the problem of providing a non-compact metallic cable that may be stored on spools between the cable forming and encapsulating operations is provided by the present invention.
There is provided in accordance with an aspect of the present invention a metallic cable suitable for reinforcing an elastomeric article comprising two or more substantially identical helical shaped metallic filaments positioned beside and against one other such that each filament is in contact with at least one other filament. The helixes formed by said filaments have a pitch length, and the filaments are twisted together such that the cable has a lay length that is at least two and one-half times greater than said pitch length.